1. Field of the Invention
The present invention relates to the removal of accumulated debris in heating, ventilation and air conditioning (HVAC) systems in buildings. In particular, it relates to a method for cleaning debris and biological growth from the inside walls of HVAC ductwork in buildings, including large or tall buildings, without having to disassemble or dismantle the ductwork or other structures behind which the ductwork is situated.
2. General Discussion of the Background
In many commercial and industrial buildings, hospitals, long-term care facilities and other institutional structures, only 10 to 15% of the indoor air is fresh. The remaining portion of the air is actually recirculated stale air. Commercial and institutional buildings provide environments where large numbers of people spend many hours every workday. In many instances, such buildings also house delicate and costly equipment and machinery. As a result, it is important that the air supply in such buildings be kept clean and hygienic.
Heating, ventilation and air conditioning (HVAC) systems are generally responsible for modifying the temperature of and circulating the air in buildings. Modern HVAC systems, if working properly, serve three basic functions: they clean and filter the air in the building, whether the air is fresh or recirculated; they add heat to or remove heat from the air; and they provide temperature regulation and air circulation. Because of these important functions, continuous maintenance of HVAC systems is important. However, most HVAC systems, particularly the ductwork thereof, are rarely inspected, and even more rarely regularly cleaned and disinfected.
Presently, the most common practice of keeping the indoor air supply clean in buildings is the periodic replacement of the HVAC filters, if the HVAC system is equipped with them. However, such practice will not prevent eventual accumulation of debris and biological growth in ductwork, especially over a long period of time. Many HVAC systems, especially in older buildings, lack filters, thereby encouraging more rapid accumulation of debris and biological growth in the ductwork. In either instance, it is important to clean and disinfect the ductwork on a regular basis.
Currently, most HVAC duct systems are cleaned using a specially adapted truck having a large vacuum unit installed thereon. A hose is connected to the vacuum unit and worked through the duct system to remove accumulated debris. Unfortunately, such truck-mounted systems have a number of drawbacks. First, the hoses and attachments thereto are simply too bulky to allow access to many sections of complex ductworks. Also, because the vacuum unit must remain attached to the truck, the method cannot generally be employed above the second or third floor of a building, leaving ductwork in high-rise buildings without any practical method for cleaning. Any suitably large vacuum units that can be detached from a truck are usually too large to transport up and down elevators, consume too much electric power and produce too much noise for use in indoor environments.
Past techniques have also typically required destructive opening of wall, ceiling or floor panels to obtain access for cleaning equipment. And, it has been necessary to cut holes, large enough for a human head, into the duct wall when it is desired to observe the cleaning equipment during use. This has further discouraged duct cleaning.
If HVAC systems in buildings or institutions are not regularly cleaned, not well maintained, or do not function properly as a result of accumulation of debris and biological growth, the occupants, equipment and machinery in the building will eventually be adversely affected. In fact, the recirculated air supply in many buildings is chronically polluted as a result of inadequate HVAC maintenance, a condition known as "Sick Building Syndrome."
Research has shown that moisture incursion into debris-laden ductwork, coupled with a higher-than-normal level of carbon dioxide, a lower level of oxygen, and temperatures within the human comfort zone, create an ideal environment for microbes to flourish. Such biological growth in the ductwork could also lead to populations of health-threatening microorganisms therein, including bacteria, viruses, yeasts and fungi. A recently publicized example is the incidence of Legionnaire's Disease which was linked to microorganism growth in a building's HVAC cooling tower. Large populations of allergy-causing molds and spores are also found in dirty ductwork. Incidents of allergies and chronic respiratory problems experienced by many workers in large buildings are thought to be caused by recirculating air kept in a contaminated state by passing through contaminated ducts.
Hence, there is a need for a method for effectively cleaning debris and biological growth from HVAC ductwork, especially in large or tall buildings. There is also a need for such a method that can be regularly and conveniently performed With minimal disruption of normal activity in the building. Further, there is a need for a method that would allow convenient disinfection of the HVAC ductwork before and/or after such cleaning, the disinfection being performed using chemicals that do not produce obnoxious odors or cause eye or respiratory irritation in nearby personnel. Further, there is a need for such a method that does not require cutting large openings in the ductwork or the destructive opening of walls and panels in order to gain access to the ductwork.